Truly relational systems support relation-valued attributes and those are the perfect means to support Optional<anything> in a database.
I wonder, if one were to query the DB, what would show up in the "birthdate table" column? I'm kind of hoping it would be zero, which would in turn be interpreted as the epoch, but sadly it would probably be null...
Not deliberately, perhaps reflexively. It just seemed the most straightforward (and interesting) interpretation of the comment in question. I hadn't seen the other comments.
> I wonder, if one were to query the DB, what would show up in the "birthdate table" column?
As I understand it, what would show up in the "birthdate table" column is a table. You would have to do a select on that table to get actual data out, and in that select you'd get either zero or one row returned.